In the world of Emerald City
Jack is a determined and faithful friend to Tip, trying very hard to help him escape. When they succeed, Jack wants to steal Mombi's dagger to finance their journey but Tip opposes the idea.
The morning after the escape, Jack is shocked to find that his best friend has been transformed into a girl.
Jack decides to take Tip to Ev, in search of someone who can produce more medication for his condition.
He finds himself drawn to his best friend in different ways than before, which puzzles him beyond reason. When it turns out that Tip is, and always has been, a girl, he tries to reassure her everything will be ok. Unfortunately, he decides to kiss Tip, which infuriates her and she accidentally pushes him off a balcony.
Jack is badly wounded after his fall. He wakes up on an operating table, with a strange woman about to start operating on him. Her name is Jane and she's an inventor and a military contractor.
Jane rebuilds Jack's body and turns him into a 'metal-man', substituting his heart, left arm and both legs with metal prosthetic. Jack is depressed that Tip left him for dead, but eventually decides to embrace the new him. That happens after he meets an aloof lady, who visites jane's workshop seeking new masks.
The lady teases Jack and taunts his lack of ambition. Jack gathers his strength and begins to practice walking with more fervour. When Jane brings him clothes and takes him for a walk, he is invited to meet the royal family of Ev. There, he sees the mysterious masked lady, who turns out to be Princess Langwidere. She has become intrigued by Jack and requested him for her own.
In the world of L. Frank Baum
Jack is a combination of two well known Oz characters: the Tin Woodman and Jack Pumpkinhead.
Pumpkinhead has been an animated being made of sticks with a pumpkin for its head, created by Tip to scare of Mombi.
Tin Woodman was one of Dorothy's companions in the first book of the series. His name was Nick Chopper and he used to be an ordinary woodman, working in the woods of Oz. He was in love with a servant of the Wicked Witch of the East, Nimmie Amee. The witch didn't want them to marry, so she enchanted Nick's axe to cut off his limbs. Each limb had been replaced with a tin equivalent and in the end only tin remained.
- Jack is depicted as a Tarot card 'Lovers' on NBC's Emerald City Facebook Page.